SEQUOIA NATIONAL PARK, Calif. — On a clear day, the view from Beetle Rock in Sequoia National Park extends west for 105 miles across the patchwork of crops in California's agricultural heartland to the Coast Mountains and the Pacific Ocean beyond.
The problem is there are few clear days, even at 6,200 feet.
Mountaintops that should offer awe-inspiring views of California's geologic grandeur often are muddled by a disorienting gray soup of smog.
"Ozone levels here are comparable to urban settings such as L.A.," said Emily Schrepf of the nonprofit advocacy group the National Parks Conservation Association as she beheld the diminished view. "It's just not right."
This is not the place to take in a whiff of fresh mountain air. Smog is so bad that signs in visitors centers caution guests when it's not safe to hike. The government employment website warns job applicants that the workplace is unhealthy. And park workers are schooled every year on the lung and heart damage the pollution can cause.
Ozone also is to blame for weakening many stands of the park's Jeffrey and ponderosa pines, leaving telltale yellowing of their long needles. Instead of absorbing carbon dioxide, they soak up ozone through the stoma in their needles, which inhibits photosynthesis. Ozone also stresses young redwood seedlings, which already face challenges to survival.
Although weakened trees are more susceptible to drought and pests, the long-term impact on the pines and on the giant redwoods that have been around for 3,000 years and more is unclear.
"It's not a great story to tell, but it's an important story to tell because you can look at us as being the proverbial canary in a coalmine," said Annie Esperanza, a park scientist who has studied air quality there for 30 years. "If this is happening in a national park that isn't even close to an urban area, what do you think is happening in your backyard?"